fpt Reference: COMMON Alignment Granularity

fpt and WinFPT Reference Manual - Command-line Commands

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COMMON ALIGNMENT GRANULARITY

Syntax:

COMMON ALIGNMENT GRANULARITY [:] <integer> [BYTE[S]]

Function:

Most systems access memory more efficiently if objects occupy aligned addresses, addresses which are multiples of 4 or 8 bytes. The command COMMON ALIGNMENT GRANULARITY specifies the spacing of aligned addresses. The alignment rules used by most compilers, and by fpt, are that:

the alignment granularity of a logical, integer or real object is the data size of the object, or the system alignment granularity, whichever is the smaller;
the alignment granularity of a complex object is the data size of the real data specification with the same precision, or the system alignment granularity, whichever is the smaller;
the alignment granularity of character variables and arrays is one byte when assigning COMMON block addresses, but access is more efficient if variables and array elements start on aligned addresses;
the alignment granularity of a record or of a derived type is the granularity of the largest object in the structure or type, or the system granularity, whichever is the smaller.

Note that the alignment granularity used by the command ALIGN OBJECTS IN COMMON BLOCKS cannot be specified interactively because addresses within COMMON blocks are computed before fpt enters interactive mode.

Where to Use this Command

Operating system command line	Yes
Configuration file, config.fsp	Yes
Specification (fsp) files, *.fsp	Yes
Interactively, to FPT> prompt	No
Interactive command files	No
Embedded in the Fortran code	No

Default

COMMON ALIGNMENT GRANULARITY : 4 BYTES

Examples:

In an FSP file for DEC Visual Fortran under Windows:

%common alignment granularity: 8
%check alignment